This section explains application program basics for any program that runs in an IMS environment. IMS programs (online and batch) have a different structure than non-IMS programs (see "Application Program Structure" on page 218). An IMS application program is always called as a subroutine of the IMS region controller and must have a program specification block (PSB) associated with it. The PSB provides an interface from the program to IMS services that the program needs to use. These services can be:
The IMS services available to any program are determined by the IMS environment in which the application is running. In This Chapter:
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